Azure DevOps Agents on AKS with KEDA Autoscaling

Overview

This repository provides a Helm chart for deploying Azure DevOps agents on Azure Kubernetes Service (AKS) with KEDA-based autoscaling. The solution ensures efficient resource utilization by scaling the agents dynamically based on pending jobs in the Azure DevOps pipeline.

Features

• Docker-based agent deployment: Uses a custom Ubuntu-based Docker image.
• Helm chart for easy deployment: Deploy the agent using Helm with configurable parameters.
• KEDA Autoscaling: Dynamically scales agents based on Azure DevOps pipeline queue length.
• Secure authentication: Uses Kubernetes Secrets for storing Azure DevOps Personal Access Token (PAT).
• Customizable configurations: Helm values allow flexibility in agent pool selection, image versions, and scaling limits.

Repository Structure

aks-azure-devops-agents/
│── docker/
│   ├── Dockerfile        # Dockerfile for the agent container
│   ├── start.sh          # Startup script for the agent
│
│── helm-chart/
│   ├── aks-azure-devops-agents/
│   │   ├── templates/
│   │   │   ├── deployment.yaml       # Deployment configuration
│   │   │   ├── scaledobject.yaml     # KEDA scaling definition
│   │   │   ├── secret.yaml           # Azure DevOps authentication secret
│   │   │   ├── trigger-auth.yaml     # KEDA trigger authentication
│   │   ├── Chart.yaml     # Helm chart metadata
│   │   ├── values.yaml    # Default configuration values

Prerequisites

• Azure Kubernetes Service (AKS) cluster
• Helm v3 installed
• KEDA installed on AKS (KEDA installation guide)
• Azure DevOps account with an agent pool
• Personal Access Token (PAT) with agent management permissions

Building and Pushing the Docker Image

1. Clone the repository:

   git clone https://github.com/Think-Cube/aks-azure-devops-agents.git
   cd aks-azure-devops-agents/docker

2. Build the Docker image:

   docker build -t <your-acr>.azurecr.io/keda-devops-agents:<tag> .

3. Push the image to Azure Container Registry (ACR):

   az acr login --name <your-acr>
   docker push <your-acr>.azurecr.io/keda-devops-agents:<tag>

Deploying with Helm

1. Update Helm values (optional): Modify helm-chart/aks-azure-devops-agents/values.yaml with your settings.
2. Create Kubernetes namespace (if needed):

   kubectl create namespace devops-agents

3. Deploy using Helm:

   helm install azdevops-agents helm-chart/aks-azure-devops-agents \
     --namespace devops-agents

Scaling Behavior

KEDA will monitor the number of pending jobs in Azure DevOps and automatically scale the number of running agents between minReplicaCount and maxReplicaCount. Scaling is managed via the ScaledObject resource in scaledobject.yaml.

Uninstalling the Deployment

To remove the agents and associated resources:

helm uninstall azdevops-agents --namespace devops-agents

Configuration

Parameter	Description	Default
replicaCount	Initial number of agent replicas	1
image.repository	Docker image repository	your-acr.azurecr.io/keda-devops-agents
image.tag	Image tag	latest
image.pullPolicy	Image pull policy	IfNotPresent
azp.url	Azure DevOps organization URL	"https://dev.azure.com/Test-Lab"
azp.pool	Azure DevOps agent pool name	"Keda-Devops-Agent"
azp.token	Base64-encoded Azure DevOps PAT	(set via Secret)
dockerVolumePath	Path to Docker socket for agent containers	"/var/run/docker.sock"
scaledObject.minReplicaCount	Minimum number of running agents	1
scaledObject.maxReplicaCount	Maximum number of running agents	5
scaledObject.poolID	Azure DevOps agent pool ID	12
triggerAuthentication.name	KEDA TriggerAuthentication name	pipeline-trigger-auth

Troubleshooting

Check Logs

kubectl logs -f deployment/azdevops-deployment -n devops-agents

Debug Scaling Issues

kubectl get scaledobjects -n devops-agents
kubectl describe scaledobject azure-pipelines-scaledobject -n devops-agents

License

This project is licensed under the MIT License.